Rail transportation is developing rapidly in China. Inter-city railway and high-speed railway as well as city subway and light rail are all under rapid construction. However, with the construction and operation of rail transportation facilities, more and more engineering problems appear. When a train passes through at a high speed, the train load is transmitted to the structure under the rail via interaction between the wheel axle and the rail. Compared with conventional fixed-point cyclic loading, the interaction between the wheel axle and the rail typically has moving effect and speed effect. As the wheel axle moves, each structure layer under the rail experiences a same loading process along the moving direction of the train. This loading characteristic is quite different from the fixed-point loading, which results in that the rail structure and the subgrade structure represent different dynamic performance. Therefore, achieving an effective simulation of load moving process of the train wheel axle is of importance to the research in actual dynamic performance of the rail transportation infrastructure. At present, the experimental methods of load simulation of a wheel axle mainly include laboratory model test and in-situ test. Since the laboratory model test is limited by model size and moving speed, it is not easy to realize high-speed moving loading for a real train. Although the in-situ test can adopt actual moving process of the wheel axle, but the environment is complicated and cannot be easily controlled, thus the repeatability is poor. The existing wheel axle dynamic load simulation apparatus, such as SBZ30 dynamic exciter which supports frequency modulation and amplitude modulation, adopts a rapid rotating eccentric block to create vertical excitation so as to achieve a high-frequency excitation of a fixed position. However, the shortcoming is: the mobility of the load of the wheel axle cannot be achieved. Another test system for simulating moving load effect of high-speed transportation adopts a forward-reverse loader, which is controlled by a centrifugal rotating motor, to drive the vertical exciter to achieve a moving loading of the wheel axle load. However, a constant moving of the wheel axle load at a high speed cannot be achieved due to the size limit.